LONDON (Reuters) - Obesity can double the risk of several
cancers, according to a study published on Friday that for the
first time also links being overweight with a number of less
common forms of the disease.

The analysis of 144 published studies incorporating some
282,000 men and women also showed that gender can make a
difference in the relationship between obesity and some
cancers, the researchers reported in the Lancet medical
journal.

The findings come after a major report from the World
Research Cancer Fund in October showed that excess body fat was
likely to cause some cancers, said Andrew Renehan, a cancer
specialist at the University of Manchester, who led the study.

ADVERTISEMENT

"This study has extended that further and reported
specifically on 20 different types of cancer," he said in a
telephone interview. "We showed an association with less common
cancers that had not been shown before."

These included blood cancers such as adult leukemia,
multiple myeloma and non-Hodgkin's lymphoma for both men and
women, he said.

Obesity is a major issue worldwide and also raises the risk
of diseases such as type 2 diabetes and heart problems. The
World Health Organisation classifies around 400 million people
as obese.

Renehan and his colleagues looked at what happened to
people whose body mass index (BMI) increased from the normal
range to overweight or from overweight to obese.

BMI is a calculation of height to weight, and the normal
range is usually considered to be 18 to 25, with more than 25
overweight and above 30 obese.

For men, the risk of thyroid cancer rose by a third and
went up 24 percent for colon and kidney cancers, the
researchers said. In women who went from normal to overweight,
the risk of gall bladder cancer rose 59 percent and kidney
cancer went up 34 percent.

"Increased BMI is associated with increased risk of common
and less common malignancies," the researchers wrote. "For some
cancer types, associations differed between sexes and
populations of different ethnic origins."

The association of cancer and obesity was largely similar
across Asia, Europe and North America, though the link between
higher body mass index and breast cancer was higher in Asia,
the researchers said.

There were also strong differences between men and women
for cancers like bowel and kidney cancers. Knowing this kind of
information could help scientists focus research on what is
exactly causing some of these cancers, Renehan said.

"We suspect there are differences in changes in hormones
due to the amount of fat cells in our body, and whether a
person is a man or a woman," he said.